An access network is used to connect a customer premises network (Customer Premises Network, CPN for short) and a backbone network. The access network may include access nodes such as a digital subscriber line access multiplexer (DSL Access Multiplexer, DSLAM for short) and a broadband remote access server (Broadband Remote Access Server, BRAS for short), or the BRAS may also be replaced with a broadband network gateway (Broadband Network Gateway, BNG for short).
Using a BRAS as an example, the BRAS may be configured to perform service processing on a received packet, where the service processing includes, for example, Internet video processing, deep packet inspection (Deep Packet Inspection, DPI for short), firewall and antivirus. With the development of the Internet, types of value-added services gradually increase, and correspondingly, the BRAS also needs to gradually enhance processing capabilities for various value-added services. In addition, each time a service upgrade is performed on the BRAS, that is, a service processing capability of the BRAS is enhanced, the BRAS needs to be powered off, and then service processing software or hardware of the BRAS is upgraded. However, the BRAS device generally supports tens of thousands to hundreds of thousands of users, and device power-off during a service upgrade interrupts an existing service, which greatly affects the users. Therefore, the prior art has poor scalability during service upgrade.